L-Transposition of the Great Arteries

Overview

L-transposition of the great arteries (L-TGA), also known as congenitally corrected transposition of the great arteries, is a form of congenital heart disease (CHD) in which blood circulation flows in the way it should, but serious problems may still exist or develop and require treatment. This condition is different from D-transposition of the great arteries (D-TGA). In L-TGA, the right and left lower pumping chambers of the heart (ventricles) are switched. The deoxygenated “blue” blood from the right atrium goes to the left ventricle and is pumped to the lungs through the pulmonary artery, and “red” blood from the left atrium goes to the right ventricle and is pumped to the major artery to the body (aorta). (Normally, the right ventricle pumps blood to the lungs.) In a baby with L-TGA, “blue” and “red” blood go where they are supposed to, so the arrangement of the heart is “corrected,” even though the pumping chambers are switched.

Symptoms

L-TGA is commonly associated with other heart problems, such as a hole in the wall between the ventricles (ventricular septal defect [VSD]) and an abnormal tricuspid valve connected to the right ventricle (Ebstein’s anomaly). These other problems contribute to the development of heart failure in children and adults with this defect. This defect is also associated with an increased risk of irregular heart rhythms, most commonly, complete heart block, which may require a pacemaker. However, if there are no other associated heart problems (VSD or Ebstein’s anomaly), some children can go undiagnosed for many years, even to adulthood.

Progression and possible complications

Patients can live to adulthood without surgery in rare instances with no other associated heart defects. However, the right and left ventricles are functionally different, with the right ventricle not designed to handle the stress of pumping against the higher pressure in the arteries of the body, which can lead to failure of the right ventricle over time. Children with L-TGA and other heart defects may require surgery early in life to help improve the heart's function.